Oil fuel burning apparatus



7 March 1970 J. P. D. HAKLUYTT 3,493,544

OIL FUEL BURNING APPARATUS 2 Sheets-Sheet 1 $42 3 /\I J 7 J17 March 1970J. P. D. HAKLUYTT 3,498,544

OIL FUEL BURNING APPARATUS Filed 001:. 3, 1967 2 Sheets-Sheet 2 UnitedStates Patent US. Cl. 239-404 6 Claims ABSTRACT OF THE DISCLOSURE A headfor a fuel oil spray burner in which fuel oil is atomised by a secondfluid such as steam is arranged with at least one fuel jet fed from afuel supply passage, the atomising fluid, preferably steam, beingintroduced to the fueljet through a passage in the form of an annularchamber formed in the head, the two fluids being mixed before ejectionfrom the head in a mixing chamber at an outer portion of the, or each,jet passage. Where a plurality of jets are provided these are preferablysymmetrically arranged around the axis of the head and the annularchamber is common to all the jets which may be arranged to be generallyconvergent or divergent or to impinge upon one another.

This invention relates to oil fuel burners and more particularly to jetspray burners in which liquid fuel is atomised by the use of a secondfluid.

In the case of atomisers where, for example, fuel oil is atomised bysteam or air, it is understood that fouling of the atomiser surfaceoccurs as a consequence of oil accumulations which carbonise. Suchfouling leads inevitably to shutdown for cleaning purposes since thedeterioration of atomisation associated with the fouling and blockage iscumulative and unacceptably serious. It is considered that theaccumulation of fouling due to oil carbonisation is governed principallyby the temperature of the surface and by the area thereof presented tothe radiation sources. In the one case, the temperature should beminimised and, in the other, the area should be minimised.

To meet these requirements a design of atomiser has been described inthe specification accompanying co-pending patent application Ser. No.634,335, now Patent No. 3,452,933. That design had been devised with thefollowing objects in view:

(a) To reduce the size of the atomiser face and to shape the atomiserhead profile in such a way that the location of the breakaway of theboundary layer is changed and thereby cooling may be improved,

(b) To reduce the bluff body effect of the atomiser head diameter byfairing the head 'so that the vertical recirculation, with its axialzone of low pressure, may be minimised,

(c) To discharge the fuel spray most advantageously, with respect to thezone of recirculation, for the purpose of mixing,

((1) To provide the maximum cooling effect which is to be derived fromthe two fluids at the atomiser face where said cooling is required inorder to keep the surface temperature below a certain point, above whichcarbonisation may occur and below which, it may not.

A two-fluid atomiser involves the introduction of separate fluids to theburner head and various proposals have been made for leading the twofluids into their respective paths so as to cause emission of jets ofthe fuel oil from the burner head and in the known arrangements ofburner complicated drillings have been necessary. It is an object of thepresent invention to provide a modified form of burner which is simplerto manufacture.

In a spray burner in accordance with the invention, the jet passage isassociated at its inner end with a supply passage for feeding one fluidand at a region intermediate its ends with an annular zone through whichthe second fluid is to be supplied, an outer portion of the jet passageforming a fluid mixing chamber wherein the two fluids are to be mixedbefore being discharged from the burner.

The jet passage will normally be straight and along the axis of theburner head.

A spray burner in accordance with the invention may comprise a pluralityof jet passages arranged in a burner head and the intermediate portionsmay then be arranged to be associated with a common annular zone throughwhich the second fluid is to be supplied. In this arrangement the innerends of the jet passages are preferably associated with a second commonannular zone through which the one fluid is to be fed.

The jet passages in the multi-jet head will normally be straight andtheir axes may be in planes containing the axis of the head, in whichcase the jets will probably be arranged to impinge against each other toproduce a divergent spray pattern.

In one form of multi-jet head according to a feature of the inventionthe axes of the jets are arranged, as in the arrangement of jetsdisclosed in the specification of the above-numbered co-pendingapplication, to be skewed, relative to each other so as to provide thedesirable divergent spray pattern; in this arrangement, however, thespray pattern may be obtained without impingement of the jets one uponanother.

Inanother form of burner in accordance with the invention, the commonannular zone for the supply of the second fluid is in the form of a verynarrow annulus extending co-axially with the burner axis and the jetpassages are arranged to pass through this thin annular zone atintermediate positions so that the issuing jets are convergent. Such ahead may, for example, be formed by the well-known investment castingmethods.

Preferably the said annular zone is used to supply atomising fluid andthe said supply passage to supply the fuel; also the inner end of thejet passage is preferably arranged to be of smaller diameter than theouter end, the passage opening to larger diameter before passing throughthe annular zone. Then, if the atomising fluid is pressurised steam, thefuel emerges from the smaller diameter as a jet and is surrounded bysteam. The eflfect of this latter arrangement is that the walls of themixing chambers are not wetted by the fuel and the formation of largedroplets of fuel is less likely to occur and may, in fact, be preventedentirely.

In order that the invention may be more fully understood, particulararrangements of burner head will now be described by way of example withreference to the accompanying drawings of which:

FIGURES 1, 2 and 3 show a burner of the single jet type, FIGURE 2 beinga view on the line IIII of FIGURE 1 and FIGURE 3 being a view on theline Il1--1II of FIGURE 1,

FIGURE 4 shows a multi-jet burner of one form, and

FIGURES 5 to 8 inclusive are illustrative of a method of forming aburner similar to the form shown in FIG- URE 4. FIGURE 5 shows a viewfrom the fluid supply end of a blank, partly machined, for the burner,FIG- URE -6 a section on the line VI-VI in FIGURE 5, FIGURE 7 a sectionon the line VIIVII in FIGURE 6 and FIGURE 8 a side elevation of thefinished form of burner.

In order that the invention may be more fully understood, onearrangement of burner head will now be de- 3 scribed by way of examplewith reference to the accompanying drawing.

Referring to FIGURES l, 2 and 3, the burner (or atomiser) head isfaired-off to a face 1 of comparatively small area. The body of the headis made in two parts as indicated in FIGURES 2 and 3, secured togetheras by brazing and the one part is formed with a recess 2 before theparts are secured together. Fuel porting 3 is provided in the head, thesupply end of this porting communicating with a bore 4 for receiving theend of a fuel supply pipe (not shown) in the burner to which the head isattached. The outer end of the fuel porting feeds into a larger diameterbore 5 that extends through the recess 2 and forms a mixing chamber 6.The recess 2 is then an annular zone for the supply of atomising fluidto the mixing chamber. Atomising fluid, such as steam, is led to theburner through a pipe (not shown) which is secured within a side bore 7leading to the porting 8 which opens into the annular zone of recess 2.

Fuel oil fed to the portion 3 passes through the annular zone 2 as afine jet and atomising fluid from the annular zone surrounds this jet sothat the fuel oil enters the mixing chamber 6 surrounded by atomisingfluid; the wall of the mixing chamber is, therefore, not wetted by thefuel oil. Mixing takes place between the oil and the atomising fluid asthey pass through the mixing chamber and the mixture emerges from thehead in a spray pattern as required, the dimensions of the portings 3and 7 of the annular zone and of the mixing chamber being chosen to suitthe conditions required. In particular, the diameter and axial depth ofthe annular zone 2 are to be such as to provide an assured distributionof atomising fluid to the mixing chamber around the periphery of thejet. It will be evident also that its axial depth may have to be limitedin some way so that it is appropriate for the jet of fuel issuing fromthe porting 3. A further bore (not shown) can be introduced at outletfrom the mixing chamber, as a small arbouring, if desired forcalibration purposes.

In the arrangement of multi-jet burner head shown in FIGURE 4, there isa fairing-off of the body to a face 9 of comparatively small area andgrouped around the face are a number of discharge orifices 10, each ofwhich forms an outlet for an atomised spray jet. Fuel is fed to anannular chamber 11 which is formed in the face of the fixing flange 12by which the head is held in the burner. Fuel supplied to the chamber 11emerges through inclined portings 13 into mixing chambers 14 in whichthe fuel is first surrounded by atomising fluid entering the mixingchamber from the annular passage 15; mixing of the fuel and atomisingfluid then takes place to enable the fuel to emerge from one of theorifices as a spray. Each system of fuel porting and mixing chamber, ofwhich only the one is shown for the sake of clarity, behavessubstantially as the single system in the arrangement of single jetsprayer described above with reference to FIGURES 1, 2 and 3, theannular passage being common to all systems in the multi-jetarrangement. Calibrating arbouring may, of course, be provided also inthe multi-jet arrangement. The annular passage 15, in the arrangementillustrated, is fed from a central feed passage 16, the head beingformed with an axial extension 17 to enable the fuel and atomising fluidfeeds to be separated for convenient attachment of the head to theburner.

The inclination of the axes of the jets is used advantageously to inducerotational velocity with benefit to the efliciency of the process ofmixing the fuel spray with combustion air in the air register with whichthe burner may be used in a boiler or other heating installation.

It will be appreciated that the diameters of the gallery 16 and of theannular passage 15 as well as the axial depth of the latter should besuch as to provide an assured supply and of adequate distribution of theatomising fluid to each mixing chamber around the whole periphery of thejet system in the chamber; as has been stated above in connection withthe arrangement of FIGURES 1, 2 and 3, it will be evident also thatthere may need to be some limitation of axial depth of the annularpassage in order that it should be appropriate for the jet of fuelissuing from the fuel porting.

The arrangement of the spray orifices comparatively close together andthe small area of the face 1 of "the head assist in overcoming thedisadvantage hitherto met of accumulation of deposits due to oilcarbonisation at the face. Also as mentioned above, the fact that themixing chamber walls are not wetted by liquid fuel assists in theprevention of large droplets of fuel which might result from suchwetting, these droplets tending to be carbonised at exit from theorifices.

FIGURES 5, 6 and 7 illustrate a method of machining a form of headsimilar to that shown in FIGURE 4, FIG- URE 5 being a view in thedirection of the arrow V in FIGURE 6, and it will be seen that it isfirst necessary to provide a cylindrical blank having a flange 18; thematerial will be that best suited in respect to use and of machining andwill probably be of steel but possibly of brass, the use of any otheralternative, however, not being ruled out.

The annular passage 19 and the gallery 20 are formed to the desireddimensions, the outer end of the gallery being opened up and internallythreaded to enable a pipe for the atomising fluid feed to be secured tothe head. The annular passage 21 is suitably milled into the wall of thegallery.

The drillings are made in the face 22 of the blank to the diameter ofthe fuel portings 2 to break into the base of the annular passage asshown for example, at B. The number, diameter and inclination of theportings will depend upon the performance required by the burner anddetails such as these are discussed in the specification of theco-pending application referred to above. These drillings will of coursebe positioned also to break through the annular passage 21.

Thereafter the drillings will be opened up from the face 22 to thediameter of the mixing chambers 24, these further drillings beingcarried through to the other side of the annular passage as shown.Finally, the outer ends are drilled to the dimensions of the arbours 25which, in the finished form shown in FIGURE 8, form the orifices, suchas indicated at A associated with entry B, in the chamfer 26superimposed on the chamfer 27 to simulate a fairing-off of the head.Slots 28 milled at intervals provide for use of a C-spanner or the likefor screwing the head on to the atomising fluid feed pipe.

It will be evident that, in either the multi-jet heads above described,the fuel oil and atomising fluid feeds may be changed over so that thefuel oil is fed through the annular passage. Although in sucharrangement the advantage of non-wetting of the mixing chamber wallswith liquid fuel is lost, there may be burner applications where wettingwill not be so disadvantageous.

If wetting is not considered to be a disadvantage in any particularapplication, it is envisaged according to a further feature of theinvention that the annular passage may be so dimensioned and/ orpositioned that the breakthrough of the second fluid porting(s) is notsymmetrical; in other words, the portings may, for example, simply breakinto the edge of the annular passage.

It will be evident that the head can be so formed that, whereas in thedesigns illustrated in FIGURES 4 and 5 to 8 the axes of the fuel spraysare convergent, there is, alternatively, either impingement of thesprays on the axis of the head, or divergence of the spray axes.Certainly, by use of the convergent or divergent design of head inaccordance with the invention, a presentation of transit paths in thegeneral spray pattern for combustion air from the outside of theaxisymmetric flame to the inside may be obtained which will be conduciveto the promo tion of flame stability.

Other points and variations within the general concept of the inventionwill be evident to those skilled in the art.

I claim: I

1. A head for a fuel oil spray burner in which the fuel oil is atomisedby means of a second fluid, at least one jet passage in said head forone fluid, said jet passage I being associated at its inner end with asupply passage for the one fluid and at a region intermediate its endwith an annular zone in the head through which the second fluid is to besupplied, the said jet passage passing through this annular zone andcommunicating therewith about substantially its entire periphery suchthat'the second fluid surrounds the one fluid as the one fluid passesthrough the said annular zone, an outer portion of the said jet passageforming a fluid mixing chamber where the two fluids are to be mixedbefore being discharged from the head.

2. A head for a fuel oil spray burner as claimed in claim 1, whereinthere is only one jet passage axially situated in a generallycylindrical body and the supply passage for said jet passage is axiallysituated at one end of said body.

3. A head for a fuel oil spray burner as claimed in claim 1, comprisinga plurality of jet passages, each jet passage being at an inclination toa plane containing the axis of the head and said jet passages beingsubstantially symmetrically disposed around said axis.

4. A head for a fuel oil spray burner as claimed in claim 1, comprisinga plurality of jet passages, each jet passage being at an inclination toa plane containing the axis of the head and said jet passages beingsubstantially symmetrically disposed around said axis and the axes ofthe jet passages being generally convergent.

5. A head for a fuel oil spray burner as claimed in claim 1, comprisinga plurality of jet passages substantially symmetrically disposed aroundthe axis of the head, the axis of each jet passage being substantiallyin a plane parallel to the said axis of the head.

6. A head for a fuel oil spray burner as claimed in claim 1, comprisinga plurality of jet passages substantially symmetrically disposed aroundthe axis of the head, the axis of each jet passage being substantiallyin a plane containing the said axis of the head and the axes of the jetpassages being generally convergent.

References Cited UNITED STATES PATENTS 1,448,106 3/1923 Binks 239404X2,303,104 11/1942 Abbey 239404 2,643,916 6/1953 White et a1. 239416.5

EVERETT W. KIRBY, Primary Examiner US. Cl. X.R. 239-4165

